The present invention relates to a mass spectrometer which detects impurity in sample gas of a low flow rate in a high sensitivity by atmospheric pressure chemical ionization.
There is known a gas analytical device using GC-PID (Gas chromatography-photo-ionization detection), or a sector type mass spectrometer using a magnetic field. Also, there is known a semiconductor sensor for detecting hydrogen.
An APCI-MS (Atmospheric Pressure Chemical Ionization Mass Spectrometer) is a device which selectively ionizes traces of components to be contained in a sample by taking advantage of an ion molecular reaction to detect in a high sensitivity, and has been used for biotechnology such as protein analysis and for impurity analysis in a semiconductor process.
In an analysis of gas which is prone to contaminate an ion source, a primary ionization part is separated from a sample inlet part, whereby clean gas is introduced into the primary ionization part to generate a primary ion; sample gas introduced into the sample inlet part is mixed with the primary ion generated in the primary ionization part to ionize an object substance to be contained in the sample gas by an ion-molecule reaction (See Japanese Patent Application Laid-Open No. 6-310091).
There has been requested a technique by which a sample is sampled from a system targeted for inspection without disturbing the system targeted for inspection as far as possible and the system targeted for inspection is inspected in a state in which the target of inspection is maintained in a dynamic state.
For example, in development of a fuel cell, in order to investigate mass balance of gas at inlet and outlet of the fuel cell for evaluating the power generation efficiency, it has become an important problem to confirm how the efficiency changes by changing parameters for temperature, flow rate and the like. In order to evaluate performance of the fuel cell, there has been increasing a request for measuring analysis of gas components at inlet and outlet of the fuel cell online.
In order to evaluate the performance of the fuel cell, highly-sensitive detectability on the order of ppm is requested. Detection sensitivity of hydrogen by a semiconductor sensor is on the order of 0.1% to 1%, and is insufficient in sensitivity. In an analysis due to GC-PID, since a separation process by GC is required, data can be obtained only at intervals of-several minutes at a minimum even if online type GC is used, and a transient operation of the fuel cell cannot be evaluated.
There has been known a sector type mass spectrometer using a magnetic field capable of continuously analyzing hydrogen concentration of the fuel cell in real time, the sensitivity is generally on the order of 0.1%, and a sampling flow rate of about (3 to 4) L/min (liter/minute) is required.
A flow rate of each of hydrogen and air necessary for an operation of the fuel cell is generally about 1 L/min, and when a sampling flow rate during an online analysis is high, a flow rate of hydrogen and air during an ordinary operation becomes different from that of hydrogen and air during an online analysis. In other words, there is a problem that it becomes difficult to accurately evaluate performance of an operation system of the fuel cell and the fuel cell.
Also, in an EI-MS (Electron Impact Mass Spectrometer) in which ionization is performed in a vacuum, since a multiplicity of fragment ions obtained by decomposing an original ion are generated during ionization, it is difficult to specify an ion derived from hydrogen in gas sampled and to determine precise concentration.
In the conventional technique, no consideration has been given in sampling while the fuel cell is maintained in a normal operating state without disturbing a system targeted for inspection, for example, an operating system of the fuel cell.